Device for pumping viscous material

ABSTRACT

An apparatus for the conveying of viscous material from a container has a conveyor pump, which has a conveyor cylinder and a conveyor piston that can be moved forward and back in the conveyor cylinder, and has a measuring device for measurement of the speed of the conveyor piston. The measuring device has a control unit for control of the conveying of the viscous material in dependence on the measured speed of the conveyor piston and a waste line is branched off from a conveying line for the viscous material, which is connected to the conveyor pump, and using the control unit the conveying line can be blocked and the waste line can be released.

The invention relates to an apparatus for conveying of viscous materialaccording to the preamble of claim 1 as well as to a method for theconveying of viscous material, in which such an apparatus is used.

Apparatuses are known that are used for the conveying of, for example,adhesives, sealing compounds or insulating compounds from a container toa processing station. They find use in particular in the automotiveindustry, when viscous materials must be applied onto vehicle bodyparts. Usually, such apparatuses have a follower plate, which rests onthe surface of the material present in the container and follows thissurface when the material level descends. For this purpose, a liftingdevice is then provided, which is used for lowering and raising of thefollower plate. The material is withdrawn from the container by means ofa conveyor pump connected to a material outlet in the follower plate,wherein the follower plate is slaved to the material surface. In thisconnection, it is also possible that the follower plate additionallypresses on the material surface so that, by virtue of this pressure, thematerial is pressed into the material outlet, while the follower platebears sealingly on a circumferential container wall. If air bubbles arepresent in the container, however, this is not perceptible prior to theapplication of the material. But when material containing air bubbles isconveyed and applied onto a workpiece, this usually causes the appliedmaterial to be unable to develop its adhesive, sealing or insulatingeffect sufficiently. Oftentimes, the structural parts coated in such away are then unfit for further processing and must be discarded asscrap.

An apparatus of the type mentioned in the introduction is known from DE197 13 938 A1. This conveyor apparatus for viscous material has ameasuring sensor, which determines the speed of the piston rod of thepump that conveys the viscous material. The measuring sensor is used tokeep the speed of the conveyor piston connected to the piston rodconstant by means of a control device. A similar apparatus is known fromDE 20 2013 009 164 U1. This apparatus has a measured-value transmitterfor control of the conveyor volume flow. However, neither of the twoapparatuses is suitable for detecting air bubbles in the material beingconveyed.

It is therefore the task of the invention to further develop anapparatus of the type mentioned in the introduction in such a way thatrejects may be prevented better.

This task is accomplished according to the invention by an apparatushaving the features of claim 1 as well as by a method having thefeatures of claim 10. Advantageous further developments of the inventionare subject matter of the dependent claims.

The invention is based on the knowledge, discovered by the Applicant,that the speed of the conveyor piston during the conveying process mayvary in a manner dependent on the material consistency. The Applicanthas found by experiments that the speed of the conveyor piston duringthe delivery stroke is constant at least within a tolerance rangeprovided the material consistency remains constant. If the materialbeing conveyed contains air bubbles, this leads to a significant changeof the speed of the conveyor piston during the delivery stroke. On thebasis of this knowledge, it is therefore proposed that the speed of theconveyor piston during the delivery stroke be measured by means of ameasuring device, so that a change of material consistency andespecially the presence of air bubbles may be inferred from a change ofthe measured speed, so that appropriate measures may be initiated. Forthis purpose, the measuring device has a control unit for control of theconveying of the viscous material in dependence on the measured speed ofthe conveyor piston. The control unit evaluates the measured values ofthe measuring device and automatically initiates measures upon adeviation of the measured speed from a predetermined target speed. Inaddition, it is provided that a waste line is branched off from aconveying line for the viscous material, which line is connected to theconveyor pump and through which the material is being fed to theprocessing station, and that the conveying line may be blocked and thewaste line released by means of the control unit. The waste line leadsexpediently to a waste container, in which the material found to beunprocessable may be diverted.

The measuring device expediently has a distance-measuring unit fortime-independent measurement of the distance traveled by the conveyorpiston. The distance-measuring unit is preferably an absolute-valuetransmitter. In addition, it is preferred that the conveyor piston isconnected mechanically to the distance-measuring unit. This may takeplace in that the conveyor pump has a piston rod, which projects fromthe conveyor cylinder, is connected in fixed manner to the piston rodand is connected rigidly by way of connecting means to a movable elementof the distance-measuring unit, and on which a drive unit alsoexpediently acts. The movement of the conveyor piston is thentransmitted directly to the movable element of the distance-measuringunit.

It may be provided that an operator-control person intervenes in theconveyor process when a significant deviation of the speed of theconveyor piston from a predetermined target speed exists. However, it ispreferred that measures are taken automatically in such a case, in orderto prevent the production of rejects.

If, in the further course of the conveying process, a speed of theconveyor piston that lies within a predetermined tolerance range aroundthe predetermined target speed is then again measured by the measuringdevice, so that it is to be assumed that the material being conveyed nolonger contains any air bubbles, the control unit automatically changesover and blocks the waste line with simultaneous release of theconveying line. For this purpose, a valve, for example a 2/2-way valve,may be provided at the place at which the waste line branches off fromthe conveying line. When the waste container is filled with material, itmay either be emptied and reused or else it is disposed of and replacedby a new, empty container.

The invention will be explained in more detail in the following on thebasis of an exemplary embodiment illustrated schematically in thedrawing, wherein

FIG. 1 shows a perspective view of a conveyor apparatus and

FIG. 2 shows a front view of the conveyor apparatus according to FIG. 1.

The apparatus 10 illustrated schematically in the drawing is used forthe conveying of viscous material such as adhesive, sealing compound orinsulating compound from a drum-like container, not illustrated in moredetail. In the exemplary embodiment shown here, the conveyor apparatus10 has a follower plate 12, which is designed to seal a container thatis open on an upper side of the container. During the conveying process,the follower plate 12 additionally bears in annularly sealing manner onthe inside face of a circumferential container wall extending to theupper side of the container. In addition, the follower plate 12 bears onthe material surface in the container. It is mounted on a lifting device14, with which it may be lowered in a manner following the descendingmaterial level in the container as well as, after emptying of thecontainer, be raised and removed therefrom. In the follower plate 12, amaterial outlet is disposed, which is not illustrated in more detail inthe drawing, and on which a conveyor pump 16 connected in fixed mannerto the follower plate 12 is attached in order to convey material fromthe container via the material outlet into a conveying line 18 leadingto a processing station. The conveyor pump 16 has a conveyor cylinder 20mounted in fixed manner on the follower plate 12 as well as a conveyorpiston—not illustrated in the drawing—which can be moved forward andback in the conveyor cylinder 20, and the linear movement of which inthe conveyor cylinder 20 sucks material through the material outlet intothe conveyor cylinder 20 and forces the material from the conveyorcylinder 20 into the conveying line 18.

The conveyor apparatus 10 additionally has a measuring device 24, withwhich the speed of the conveyor piston during the delivery stroke may bemeasured. The measuring device 24 has a distance-measuring unit in theform of an absolute-value transmitter 26, the housing of which ismounted on the lifting device 14. A piston rod 28 connected in fixedmanner to the conveyor piston is guided upwardly out of the conveyorcylinder 20 and by means of connecting rods 30 is connected rigidly to amovable element of the absolute-value transmitter 26. Thedistance-measuring device 24 additionally has a control unit 32, whichcontrols the conveying of the viscous material in dependence on themeasured speed of the conveyor piston. The control unit 32 recognizeswhen the measured speed of the conveyor piston lies outside a tolerancerange by a predesignated target speed, which suggests that theconsistency of the material being conveyed has changed so much that itssuitability is in question. In this case, the control unit 32 operates avalve 34, so that the material being conveyed is conveyed not to theprocessing station but instead into a waste line 36, which is branchedoff from the conveying line 18 and leads to a waste container 38. If thecontrol unit 32 recognizes that the speed of the conveyor piston againlies within the tolerance range, it operates the valve 34 yet again andthe viscous material is again conveyed via the conveying line 18 to theprocessing station.

In summary, the following is to be stated: The invention relates to anapparatus 10 for the conveying of viscous material from a container,with a conveyor pump 16, which has a conveyor cylinder 20 and a conveyorpiston that can be moved forward and back in the conveyor cylinder 20.According to the invention, a measuring device 24 is provided formeasurement of the speed of the conveyor piston.

1. An apparatus for the conveying of viscous material from a container,with a conveyor pump (16), which has a conveyor cylinder (20) and aconveyor piston that can be moved forward and back in the conveyorcylinder (20), and with a measuring device (24) for measurement of thespeed of the conveyor piston, wherein the measuring device (24) has acontrol unit (32) for control of the conveying of the viscous materialin dependence on the measured speed of the conveyor piston and wherein awaste line (36) is branched off from a conveying line (18) for theviscous material, which line is connected to the conveyor pump (16), andby means of the control unit (32) the conveying line (18) can be blockedand the waste line (36) can be released.
 2. The apparatus according toclaim 1, wherein the measuring device (24) has a distance-measuring unit(26) for time-independent measurement of the distance traveled by theconveyor piston.
 3. The apparatus according to claim 2, wherein theconveyor piston is connected mechanically to the distance-measuring unit(26).
 4. The apparatus according to claim 3, wherein the conveyor pump(16) has a piston rod (28), which projects from the conveyor cylinder(20), is connected in fixed manner to the conveyor piston and isconnected rigidly by way of connecting means (30) to a movable elementof the distance-measuring unit (26).
 5. The apparatus according to claim2, wherein the distance-measuring unit (26) is an absolute-valuetransmitter.
 6. The apparatus according to claim 1, wherein the wasteline (36) leads to a waste container (38).
 7. The apparatus according toclaim 1, further comprising a follower plate (12) for sealing of thecontainer on an open upper side of the container, which has a materialoutlet to which the conveyor pump (16) is attached.
 8. A method forconveying of viscous material from a container by use of the apparatus(10) according to claim 1, wherein the viscous material is conveyed inthe conveying line (18) when the measured speed of the conveyor pistonlies in a predetermined tolerance range around a predetermined targetspeed, and wherein the viscous material is conveyed in the waste line(36) when the measured speed of the conveyor piston lies outside thetolerance range.